The use of fusing machines to achieve a splice or pigtail connection between conventional stranded lead wire and solid, insulated wire has become quite widespread since this is a highly advantageous technique for achieving a quick and uniform joint during a manufacturing operation. In fact, where a tinned, stranded lead wire is to be connected to a magnet wire of the type employed in motor windings or frequently as connections to transducers or the like, it is only through a fusing operation that such connections can be made if the magnet wire is not to be first stripped of its clear insulating coating. This occurs because such a coating as is employed in windings for motors and the like will not break down or vaporize at temperatures below a value which typically may be of the order of 200.degree. C. Therefore, since a stripping of the clear coating on magnet wire tends to be somewhat onerous in a manufacturing process because the same is usually comprised of varnish or the like, the use of fusing equipment for such applications as joining conventional tinned lead wire to magnet wire from a motor winding, transducers which are similarly wound such as speakers or microphones, and circuit elements such as core inductors or the like, has become widespread, In addition, fusing apparatus is also employed to connect terminals and terminal lugs to magnet wires in manufacturing processes to insure a strong, uniform joint which is fused and conductive throughout so that the same is highly reliable.
In U.S. application Ser. No. 566,708, as filed in the name of Edward D. Riordan on Dec. 29, 1983 and entitled FUSING MACHINE, METHOD AND ELECTRODE SET and assigned to the assignee of the instant application, there is disclosed a fusing machine, method and electrode set which is highly advantageous for most applications for achieving a splice or pigtail connection between a conventional stranded wire whose end to be connected has typically been stripped and tinned and a magnet wire having a clear insulating coating remaining thereon. However, in certain applications it has been found that the fusing operation being conducted can result in an overheating of the electrode set within the fusing apparatus and a joint between wires which is not uniform throughout.
In the case of a non-uniform joint, fusing frequently occurs between a peripheral portion of the magnet wire and only a few strands within a stranded wire to be joined so that, in effect, a substantial portion of the cross-section of the stranded wire is not made part of the joint. This typically occurs when the magnet wire being employed is thick or is coated with an insulating material exhibiting extremely high temperature tolerance. The result is generally a weak, unreliable connection which is subject to early failure.
Furthermore, as is becoming increasingly the case, when lead wire, in the form of stranded wire, solid wire or magnet wire, is extremely thin conventional fusing apparatus, as well as that disclosed in U.S. application Ser. No. 566,708, supra, will often result in such substantial heat being applied to the stranded or solid wire that insulation thereon outside of the area of the joint will frequently be destroyed during the fusing operation or the wire is otherwise deformed. In the case of thin magnet wire, breaking of this wire outside of the area of the joint may also occur. This leads to unreliability in the resulting product and frequently early failure thereof. For the very same reasons, such fusing equipment may not be generally employed to connect lead or magnet wire to semiconductive devices such as diodes without providing heat sinks for the semiconductive device to avoid the destruction thereof.